Sonographic findings of extensor digiti minimi triggering caused by thickened extensor retinaculum.

Trigger finger is a common well recognized condition and involves the flexor tendons at the A1 pulley in the palm. Triggering of the extensor tendons is a very rare clinical entity. We report a rare case of extensor triggering of little finger caused by constriction of the extensor digiti minimi by a markedly thickened extensor retinaculum (ER) at the wrist, well delineated dynamically by real-time high-resolution ultrasound. The patient underwent release of thickened ER and was asymptomatic immediately.